Gas separation – Multiple bag type filters in chamber – Gas flow from inside to outside of filter
Reexamination Certificate
2001-09-19
2003-07-15
Smith, Duane (Department: 1724)
Gas separation
Multiple bag type filters in chamber
Gas flow from inside to outside of filter
C055S341400, C055S341500, C055S341600, C055S341700, C055S523000, C096S004000, C096S008000, C096S010000, C210S323200, C210S340000, C210S346000, C210S486000
Reexamination Certificate
active
06592641
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to hot gas cleanup systems and more particularly to such systems that separate out, in addition to particulate matter, a molecular component of the gas.
BACKGROUND OF THE INVENTION
Hot gas filtration systems are key components in advanced coal or biomass-based power plants. The hot gas filtration systems protect the downstream heat exchanger and gas turbine components from particle fouling and erosion, and clean the process gas to meet emission requirements. When hot gas filtration systems are installed in either pressurized fluid-bed combustion (PFBC), pressurized circulating fluidized-bed combustion (PCFBC), or integrated gasification combined cycle (IGCC) plants, lower downstream component costs are projected, in addition to improved efficiency, lower maintenance, and elimination of additional and expensive fuel and/or flue gas treatment systems. As a critical component, long term performance, durability and life of the porous ceramic and/or metal filter elements and associated high temperature, primary and secondary gasket seals are essential to the successful operation of hot gas filtration systems in advanced combustion and gasification applications. Utilization of this advanced barrier filter system concept extends as well to industrial applications where enhanced purity of product, separation of materials, and emissions control can be realized.
Examples of prior art hot gas filtration systems can be found in U.S. Pat. Nos. 5,433,771 and 5,876,471 assigned to the assignee of this application. The prior art teaches, as illustrated in
FIG. 1
, the use of a filter apparatus
20
for separating particulate matter from a gas stream. This apparatus includes a pressure vessel
22
in which there are mounted a plurality of clusters comprising a plurality of filter element arrays
26
. These filter element arrays
26
include a plurality of “candle filter elements”
28
.
The pressure vessel
22
has a dome shaped head
30
and body
32
. The dome shaped head
30
terminates in a co-linear axial tubular extension
34
that defines an exit opening or nozzle
36
for the filtered gas to be removed from the vessel
22
. The body
32
of the pressure vessel
22
includes an unfiltered gas inlet
25
, an upper portion
38
that interfaces with the domed head
30
, having a generally circular cylindrical shape, that is joined by a frusto-conical ash hopper
40
at the end opposite the domed head
30
. The ash hopper
40
, which is designed to receive the particulate matter, terminates at its opposite end in a linear coaxial extension that defines an opening or nozzle
42
that is connectable to an ash discharge line. A plurality of ports
44
extend from the dome shaped head
30
. The ports
44
provide a site for inserting instrumentation and for viewing the interior of the domed shape head
30
during shutdown periods. Through each port
44
tubes
46
for supplying a back pulse burst of gas for cleaning the candle filters
28
can be placed.
Referring to
FIG. 2
, the pressure vessel
22
includes a tube sheet
48
which separates dirty and clean sides of the system, and which supports vertical clusters
27
best shown in FIG.
1
. Each cluster
27
is comprised of one or more manifolds or plenums
29
which in turn supports arrays
26
containing filter elements
28
, as best viewed in FIG.
2
. Each plenum
29
comprises an upper plate
50
and a lower plate
52
. In accordance with the present invention, each filter element
28
is held within a filter holder and gasket assembly
60
(best shown in
FIG. 3
) and coupled to the corresponding lower plate
52
of the plenum
29
. Each cluster support pipe
58
, as shown in
FIG. 2
, is supported parallel to the central axis of the pressure vessel
22
. A dust shed or particle deflector
56
having a generally frusto-conical shape is attached above each plenum
29
.
The prior art teaches the use of the filter holder and gasket assembly
60
as shown in
FIG. 3
with a conventional thick-wall hollow tube monolithic ceramic. Fixturing for an alternate porous metal candle filter
28
, and/or a thin wall composite and/or filament wound candle filter
28
is taught in U.S. Pat. Nos. 5,876,471, 5,944,859, 6,123,746 and 6,273,925. The filter holder and gasket assembly
60
provide a particulate barrier seal between the clean gas and dirty gas surfaces of the filter element
28
. In
FIG. 3
, the filter holder and gasket assembly
60
for a conventional thick wall ceramic candle filter is shown assembled. The filter holder and gasket assembly
60
comprise a filter housing
62
having a peripheral sidewall
64
which defines an interior chamber
66
, a fail-safe/regenerator device
68
, permanently or removeably installed within the interior chamber
66
, an annular spacer ring
70
permanently or removeably installed within the interior chamber
66
, a gasket sock or sleeve
72
, a top or topmost compliant gasket
74
, a bottom or bottom-most compliant gasket
76
and a cast nut
78
.
Preferably, the spacer ring
70
is permanently mounted to the fail-safe/regenerator to produce a single unit that is placed within the interior chamber
66
of the filter housing. In this case, the spacer ring
70
may be welded in abutment with the fail-safe/regenerator
68
to secure the fail-safe/regenerator
68
unit and to prevent the filter element
28
from moving and contacting the filter housing
62
, thereby preventing possibly damage to the filter element
28
. When the fail-safe/regenerator
68
is not incorporated into the filter housing
62
, then only the spacer ring
70
will be securely mounted within the filter holder interior chamber
66
. Alternately, the fail-safe/regenerator device
68
may be removeably mounted within the housing interior chamber
66
with the spacer ring
70
permanently mounted within the housing interior chamber
66
. The fail-safe/regenerator device
68
is provided to prevent matter from travelling from the dirty gas stream to the clean gas area of the pressure vessel
22
if a candle filter element fails, is damaged or breaks. Additionally, the fail-safe/regenerator
68
will heat the back pulsed gas, which is generally cooler than the gas stream to prevent the filter element
28
from enduring thermal fatigue or cracking.
The fail-safe/regenerator unit
68
, more fully described in U.S. Pat. No. 5,433,771, is a tubular metal unit
51
having perforated metal plates
53
welded to each end. Fine mesh screens
54
, and heavy mesh support wires
55
are positioned adjacent to the metal plates
53
within the interior of the tubular member
51
. The fine mesh screens
54
serve as the fail-safe mechanism to capture and retain fines, and plug in the event that a candle filter
28
fails, is damaged or breaks. The heavy mesh support wires
55
provide structure to support the fine mesh screens
54
. Within the interior of the fail-safe/regenerator
68
raschig rings
73
are contained between the heavy mesh support wires
55
, to heat incoming back pulsed gas that is used to clean the candle filters
28
, which are part of the filter arrays
26
within the pressure vessel
20
.
Applicants have found that in many hot gas filtering applications it is desirous to separate constituent components of the filtered gas such as in syngas applications. This can be achieved through the use of micro-porous membranes. A micro-porous membrane particularly suited to high temperature applications for separating hydrogen from a gas stream is particularly described in co-pending application Ser. No. 09/822,927 filed Mar. 30, 2001. Use of such membranes have been considered feasible in the temperature range of 600-1600° F. (315-870° C.). Hydrogen separation from syngas is a processing step having major market potential today in integrated refinery applications and for chemical synthesis. The high market potential of hydrogen production and the complementary aspects of producing a syngas concentrated in CO
2
for removal and isolation, make the selection and implementation o
Alvin Mary Anne
Lippert Thomas E.
Newby Richard A.
Pham Minh-Chau T.
Siemens Westinghouse Power Corporation
Smith Duane
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